The present invention relates to microelectromechanical systems in general, and more particularly, to microelectromechanical optical switches.
MicroElectroMechanical (MEM) technology has been used in a wide range of applications. For example, MEM devices have been used in optical switching systems to switch optical radiation from the switch inputs to selected switch outputs. Conventional optical switches, sometimes referred to as Optical Cross-Connect (OXC) switches can include an Nxc3x97N array of reflectors to reflect optical radiation from any switch input to any switch output. Each input and output can be aligned with an associated row or column of the array. For example, in a 2xc3x972 MEM OXC switch having 2 inputs and 2 outputs, the first and second inputs can be aligned with first and second rows of the 2xc3x972 array and the first and second outputs can be aligned with first and second columns of the 2xc3x972 array. In operation, a selected reflector of the 2xc3x972 array can be used to reflect the optical radiation from any switch input to any switch output.
The selected reflector can be located in the array where the column associated with input and the row associated with the output intersect. The selected reflector can be placed in a reflecting position to reflect the optical radiation from the input to the selected output. At least some of the other reflectors can be placed in non-reflecting positions so as not to impede the propagation of the optical radiation from the input to the selected reflector and to the output.
As the number of inputs and outputs of conventional MEM OXC switches increase, so may the number of reflectors used to provide the operations thereof. The number of reflectors, R, used in a conventional Nxc3x97N OXC generally can be expressed as:
xe2x80x83R=N2
Where N is the number of inputs and outputs of the switch. For example, a 2xc3x972 OXC switch may include 4 reflectors, a 3xc3x973 OXC switch may include 9 reflectors, and a 4xc3x974 OXC switch may include 16 reflectors etc. A conventional 2xc3x972 MEM OXC 100 is shown in FIG. 1.
Referring to FIG. 1, each of the reflectors 101-104 includes a reflective surface 105-108 and can be placed in either a reflecting or non-reflecting position. Accordingly, the MEM OXC 100 can be placed in 2N2 possible configurations, where each configuration can be defined as a unique combination of reflector positions. Unfortunately, it may not be possible to use all of the 2N2 configurations. In particular, some of reflector configurations may include configurations where two or more reflectors in a row or column of the array are in the reflecting state, thereby blocking the reflection of the optical radiation from the input to the output. For example, to switch optical radiation from input I1 to output O1, reflectors 102 and 103 are placed in non-reflecting positions to allow the optical radiation to propagate from input I1 to output O1. Therefore, some of the possible 2N2 configurations may not allow the MEM OXC to operate properly.
Unfortunately, as the number of inputs and outputs increase, so may the number of reflectors. For example, a 5xc3x975 OXC switch may use 52 reflectors, a 6xc3x976 may use 36 and so on. It is known to reduce the number of reflectors by providing reflectors with reflective surfaces on opposite sides of the reflectors as shown, for example, in FIGS. 2A and 2B. According to FIGS. 2A and 2B, one reflector 200 can operate as a 2xc3x972 MEM OXC switch 201. In particular, inputs I1 and I2 are oriented in first and second directions 225, 235 relative to the reflector 200. Outputs O1 and O2 are oriented in the first and second directions respectively relative to the reflector 200. When the reflector 200 is in the reflecting position, as shown in FIG. 2A, optical radiation can be reflected from input I1 to output O2 and from input I1 to output O1. When the reflector 200 is in the non-reflecting position, as shown in FIG. 2B, optical radiation can pass from the input I1 to the output O1 or from the input I1 to the output O2. Accordingly, the reflector 200 can operate as a 2xc3x972 MEM OXC switch 201. Notwithstanding the above, there continues to exist a need to provide improved OXC switches having a reduced number of reflectors therein.
Embodiments of the present invention can allow MicroElectroMechanical (MEM) Optical Cross-Connect (OXC) switches to have a reduced number of reflectors by providing N inputs to the OXC switch and N outputs from the OXC switch, where N is at least 3. The Nxc3x97N OXC switch provides N! states, wherein the N! states optically couple any one of the N inputs to any one of the N outputs. The Nxc3x97N OXC switch also includes a number of switching nodes that are selectively optically coupled to the N inputs and N outputs. Each of the number of switching nodes is configurable in at least one of a switching configuration and a pass-through configuration to provide selectively switched optical radiation therefrom and wherein the number of switching nodes is equal to ceiling [ln(N!)/ln(2)] to provide the N! states of the Nxc3x97N OXC switch. The Nxc3x97N OXC switch further includes at least one optical transmission apparatus coupled to at least two of the switching nodes.
Reducing the number of switches used in an Nxc3x97N MEM OXC switch may allow for Nxc3x97N switches that use fewer actuators than conventional Nxc3x97N switches. In particular, conventional Nxc3x97N switches may include N2 switches to provide N! switch settings. Such a conventional switch may use, for example, as little as 0.04% of the 2N2 states for a 4xc3x974 switch. In contrast, Nxc3x97N switches according to the present invention can include ceiling [ln(N!)/ln(2)] reflectors. Such a 4xc3x974 switch according to the present invention may utilize 75% of its respective possible states. For example, a conventional 4xc3x974 switch may include 16 switches whereas an Nxc3x97N switch according to the present invention may include 5 switches. Also, fewer switches and actuators may be formed on a smaller substrate area, thereby allowing a reduction in the footprint of an Nxc3x97N switch according to the present invention.
In other embodiments according to the present invention a 2xc3x972 array of reflectors is arranged in first and second rows and first and second columns. First, second and third inputs to the Nxc3x97N OXC switch are selectively optically coupled to at least one of the 2xc3x972 array of reflectors. First, second and third outputs from the Nxc3x97N OXC switch are selectively optically coupled to at least one of the 2xc3x972 array of reflectors. Related method embodiments for all of the above described OXC switches also may be provided. Accordingly, reduced numbers of reflectors and/or actuators may be used in optical cross connect switches.
In other embodiments according to the present invention, an Nxc3x97N OXC switch includes a first movable reflector that is optically coupled to a first input and a second input. The first movable reflector receives first optical radiation in a first direction via the first input and receives second optical radiation in a second direction via the second input. The first moveable reflector provides the first optical radiation to a first output therefrom that propagates in the first direction when the first moveable reflector is in a non-reflecting position and provides the second optical radiation to the first output that propagates in the first direction when the first moveable reflector is in a reflecting position. A second movable reflector provides optical radiation from a third input thereto in the second direction to a second output therefrom when the second moveable reflector is in the non-reflecting position. An optical transmission apparatus optically couples the first output of the first moveable reflector to the third input of the second movable reflector and changes the direction of propagation of the optical radiation at the first output from the first direction to the second direction at the third input.
In other embodiments according to the present invention, the optical transmission apparatus is a fixed reflector. In yet other embodiments according to the present invention, the optical transmission apparatus is a linear or curvilinear waveguide.